A horticultural lovefest takes over a container in the rooftop garden, as bees flit around a budding Meyer lemon tree and then nuzzle up against a cherry tomato plant. A prolific thyme plant also competes for the bees' affection, its gorgeous purple flowers waving around in the wind, beckoning the urban bees to come hither.

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"It's time for a little talk about the birds and the bees," Fred Bové joked, as he explained to me how the plants illustrated the permaculture principle of garden guilds, groupings of vegetation in which each plant supports the other plants around it.

Each container on The Chronicle's rooftop is filled with plants that co-exist, sharing the same soil, water and light. They even share the affections of the birds and the bees.

Most garden guilds borrow heavily from Mother Nature. With thoughtful and protracted observation, permaculturists observe the conditions that a plant naturally thrives in, and use that information to create beneficial relationships among plants.

With just a few tweaks to our existing garden design, Bové and Kevin Bayuk from the San Francisco Permaculture Guild have helped me transform The Chronicle's rooftop garden from a ragtag group of planters into a collection of mini ecosystems.

Emulating nature on a SoMa rooftop may seem far-fetched, but garden guilds have helped us maximize production in a limited space, a huge challenge for container gardening. By mimicking nature, our plants now share nutrients, light and water, and even attract pollinators and repel unwanted pests for one another.

"Every element in the guild serves more than one function, and every function is served by more than one element," explained Bayuk, as he gave me my elementary-school-level education on permaculture.

Despite all the wonky talk about elements and functions, creating garden guilds can be easy.

For example, one of the planters on our rooftop has an espaliered apple tree, runner beans, strawberries and spinach. The low-lying strawberries act as ground cover, which helps the soil retain moisture, and the nitrogen-fixing runner beans feed the soil underneath the apple tree. And when the runner beans get tall, they can climb the lower branches of the apple tree as well as a nearby trellis. The shade-loving spinach thrives in the shadows created by the apple tree and the runner beans (see cover illustration).

Though the term permaculture wasn't coined until the 1970s, the practice borrows many of its techniques from cultures that have been tilling the earth for centuries. The American Indians, for example, have long planted beans, squash and corn together, a grouping commonly referred to as the Three Sisters. In addition to providing the American Indian diet with a complete protein, the crops can be stored without refrigeration through the winter.

For one of our garden guilds on the rooftop, we borrowed heavily from American Indian wisdom, planting Hubbard squash alongside bush beans and blue corn (see cover illustration). The squash leaves provide a cool, moist ground cover that also suppresses weeds, and when mature, the beans climb up the corn stalks. We also added sunflowers, which provide a windbreak and act as a trellis for the beans.

All of the elements, once harvested, produce biomass that can be chopped and added to the already nitrogen-enriched soil, ensuring a head start on next year's crop.

When the plants share resources, they are happier and more productive. "The yield of a polyculture will also surpass that of a monoculture," explained Bayuk.

"It's so easy when you know what's going on," says Bové.

The permaculture philosophy of sharing resources and supportive relationships can work outside the garden too. For our next project? Maybe we'll change the world by getting people to create guilds at home and at work too.

Then life would really be easy.

Orchard guild

The Chronicle's rooftop garden has this example of an orchard guild, with the apple tree as the centerpiece of a complex series of interrelationships with the other plants.

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Garden guilds

Though the idea of interplanting is familiar to many home gardeners, permaculture guilds take companion planting a step further by encouraging beneficial relationships between plants. Here are a few guilds that are in The Chronicle's rooftop garden.

-- Meyer lemon tree, Chinese snap peas

-- Pear tree, cherry tomatoes, parsley, sorrel, basil

-- Meyer lemon tree, cilantro, cherry tomatoes, French scorzonera

-- Vietnamese cilantro, lemongrass, magrut lime tree, tatsoi

-- Rainbow chard, onions, ceanothus, leeks, garlic

-- Oca, yacon, amaranth, Peruvian ground cherry

Here are a few simple ways to incorporate the guilds into any home garden.

-- Stagger planting times.

-- Put plants with similar watering and light needs together.

-- Think of your garden in layers: Start with the biggest, tallest crop and then think about which midlevel and low-level plants would create beneficial relationships.

-- Consider natural successions of crops. For example, scarlet runner beans can be followed by mache in wintertime. - J.T.